1. Technical Field
The present disclosure relates to a toner, a method of manufacturing the toner, a developer including the toner, a toner container including the toner, an image forming method using the toner, and a process cartridge including the toner.
2. Description of Related Art
Toner for use in electrophotographic image forming apparatuses or electrostatic recording devices generally comprises colored particles in which colorants, charge controlling agents, etc., are dispersed in a binder resin. Toner is manufactured by various processes, such as pulverization process and suspension polymerization process.
Pulverization process can use only limited kinds of materials and cannot provide a high level of toner yield. It is generally difficult for pulverization processes to uniformly disperse colorants, charge controlling agents, etc., in thermoplastic binder resins. Therefore, a toner obtained by a pulverization process may be poor at fluidity, developability, durability, and image quality.
Binder resins generally occupy 70% or more of toner composition. Most binder resins are derived from petroleum resources now being exposed to depletion. Petroleum resources cause a problem of global warming because they discharge carbon dioxide into the air when consumed. On the other hand, binder resins derived from plant resources have been proposed and used for toners. Because plant resources have incorporated carbon dioxide from the air in the process of growing, carbon dioxide discharged from plant resources is merely circulated between the air and plant resources. Thus, plant resources have the potential to solve the problems of both depletion and global warming. JP-2909873-B2 (corresponding to JP-H07-120975-A), JP-H09-274335-A, and JP-2001-166537-A each describe a toner including a polylactic acid as a binder resin but the toner is obtained by a pulverization process.
Polylactic acid is obtainable by a dehydration condensation of lactic acid or a ring-opening polymerization of a cyclic lactide of lactic acid. Polylactic acid is adaptable for non-pulverization toner manufacturing processes in which a binder resin is dissolved in an organic solvent and the resulting solution is suspended in an aqueous medium (hereinafter “dissolution suspension processes”). Polylactic acids consisting of L-form or D-form have high crystallinity. Such polylactic acids are poorly soluble in organic solvents, and therefore they cannot be adaptable for the dissolution suspension processes. JP-2008-262179-A describes that a mixture of L-form and D-form polylactic acids has a lower crystallinity and an improved solubility in organic solvents. However, such a mixture of L-form and D-form polylactic acids may be still less stable in solubility than polyester resins that are soluble in ethyl acetate.
JP-2010-122667-A also describes a toner including a polylactic acid, but the toner also includes a styrene-acrylic resin.